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December 17, 2007 by Blogging Developer

Doing many string concatenation operations can be a major hit on performance even in Javascipt.

Using + to concatenate string pieces into a huge string is not the correct and the only way. Since string concatenation results in too many intermediate strings and concatenation operations, it performs poorly.

A better approach for string concatenation is using Array.join(), which joins all array elements into one string:

var tmp = [];
for (/* each piece */)
{
tmp.push(piece);
}
str = tmp.join('');
return str;

This method doesn't suffer from the intermediate strings, and executes faster with high number of concatenation operations.

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Tag : javascript, array.join, string concatenation

Categories : JavaScript | Tips

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Comments

May 8. 2008 06:30

That is definitely true for Internet Explorer, but in Firefox it is actually faster to use the + to concatenate a bunch of strings than it is to put all the pieces in a temporary array and use the array.join method. In IE the difference is huge though, so it may even be worthwhile to do a browser check before deciding which method to use.

Nicholas Hoza

July 8. 2008 18:06

What about concat() method (in String class) ?

bigkif

July 9. 2008 12:10

I don't see why my comment has been deleted :p ... Please tell me what is wrong in my comment (maybe my english ?) instead of deleting it without warning.

My question was : what about using concat() on String class ? This should be the best way to do this...

bigkif

July 11. 2008 09:36

Hi bigkif,

Thanks for your comment.
Actually, Array.Join is the fastest way to concatenate strings.

Cheers,
Blogging Developer

Blogging Developer

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JavaScript Array.Join vs String Concatenation - Avoid String Concatenation's Major Hit on Performance

December 17, 2007 by Blogging Developer

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